Rubber process



Patented Oct. 31, 1939 UNETED STATES PATENT OFFliCE No Drawing. Application June 14, 1937, Serial No. 148,217. In Great Britain June 27, 1936 4 Claims.

This invention relates to threads and fabrics and processes for forming threads and fabrics, such as are described in my British Patents Nos. 447,972, 448,098, 449,314, 449,462, 459,434 and 467,083, as well as to films, sheets, tapes or other rubber products which might be formed in analogous ways to the thread. The foregoing patents describe processes in which there is incorporated into the rubber or rubber-like materials from which the threads are made, substances such as glue or gelatine which reduce the extensibility of the threads.

The object of the invention is to provide means or processes for controlling the removal of such inhibiting substances, whereby threads or fabrics may be used or treated in various processes and yet may remain relatively inextensible, and extensibility restored when desired.

According to the invention the process of treating threads, tapes, films, sheets or fabrics of rubber wherein glue or gelatine has been incorporated therein in order to reduce the extensibility of the products and wherein the said glue or gelatine has been rendered partly or wholly insoluble by treatment with formaldehyde, consists in subjecting the products to the action of an aqueous solution of urea.

The invention also consists in products whenever obtained by the process described.

Other features of the invention are hereinafter described and claimed in the appended claims.

The insolubilised glue or gelatine may be removed from the thread, tapes, etc., either as such or when they are combined with textiles in the form of cloths and fabrics. The threads, etc., may be made by any known process and thus the rubber may be latex rubber or masticated rubber.

In carrying the invention into effect in one form by way of example, a thread is formed for example by the extrusion of an aqueous emulsion of rubber such as compounded latex which has glue incorporated in it, and such glue is rendered insoluble or partially insoluble by means of formaldehyde. One method of effecting the formaldehyding is to introduce a quantity of formaldehyde in the coagulant into which the thread is extruded. Another is to have about 5 per cent. of 40 per cent. formaldehyde solution present in the alcohol in which the thread is collected after extrusion. It does not apparently matter when the formaldehyde treatment is effected and if desired this treatment can be carried out by passing the thread through a solu tion of formaldehyde in either water, alcohol or the formaldehyde may be employed in the form of a gas. When dry, this treated thread is less extensible than the untreated thread and is more resistant to humidity. Boiling the thread in water will not, however, deset that is to say restore the elasticity of such thread.

To carry out the desetting of this thread when it has been woven or knitted into a fabric, the following procedure is adhered to:

The fabric is left soaking over night in a 10 per cent. aqueous solution of urea when it is then boiled in the urea solution for half an hour, or if unvulcanised thread is used any longer time to bring about the vulcanisation of the thread. The strength of the urea solution can be varied and the stronger the solution, the shorter time is necessary to solubilise the hardened glue.

I claim:

1. The process of treating fabric containing rubber threads which comprise rubber with which glue has been incorporated to render the threads relatively inextensible and in which the glue has been rendered insoluble by treatment of the threads with formaldehyde, consisting in subjecting the fabrics to treatment in an aqueous solution of urea whereby the glue content of the thread is rendered soluble and the rubber threads are rendered elastic.

2. The process as claimed in claim 1 wherein the treatment comprises placing the fabric in a 10 per cent. aqueous solution of urea, and boiling the fabric in the said solution whereby elasticity is restored.

3. The process of treating fabric containing rubber threads which comprise unvulcanized rubber with which glue has been incorporated to render the threads relatively inextensible and in which the glue has been rendered insoluble by treatment of the threads with formaldehyde, consisting in subjecting the fabrics to treatment in an aqueous solution of urea whereby the glue content of the thread is rendered soluble and the rubber threads are rendered elastic.

4. The process as claimed in claim 3 wherein the treatment comprises placing the fabric in a 10% solution of urea and boiling the fabric in the said solution to restore elasticity and effect vulcanization.

THOMAS LEWIS SHEPHERD. 

